1. Department of Endodontology and Operative Dentistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
2. Department of Restorative Dentistry, Faculty of Dental Medicine, Hokkaido University, Kita13 Nishi7, Kita-ku, Sapporo 060-8586, Japan
3. OBT Research Center, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
4. Department of Endodontology, Kyushu University Hospital, Fukuoka 812-8582, Japan